Aluminum house siding protects your home from the elements without becoming water logged or rotten. To keep the aluminum siding looking clean, remove stains as soon as they occur -- including latex paint that may have dripped. The longer paint spots sit on aluminum siding, the harder they'll be to remove, as latex paint hardens and adheres to the aluminum the longer it dries.
Latex paint is water-based, which means you can use water to remove latex paint spots, especially if the paint was just recently dripped and is still somewhat wet. Always keep a wet rag in your pocket when working with latex paint, and wipe it over the spills on your aluminum siding.
Liquid Dish Soap
Liquid dish soap will enhance water's ability to remove paint spots and is the next best option if water did not work to remove the stain. To use it, add a few drops liquid dish soap to water and mix until it's sudsy. Then, scrub the solution into the aluminum siding until the stain is gone. If this doesn't work, let the solution sit on the latex paint stain for a while until it's soft, and then scrub it off with a soft-bristled brush. Never use stiff-bristled, as this type scratches aluminum surfaces.
Rubbing alcohol is a mild solvent that will loosen and soften very old latex paint spots from aluminum siding. To use it, soak a sponge in rubbing alcohol and hold it over the paint stain for several minutes. Remove the sponge and scrub the paint spots up with a soft-bristled scrubbing brush. If the latex paint stain is particularly tough, use a paint scraper and more rubbing alcohol. Alcohol is flammable, so always practice caution when using it -- and rinse it from the aluminum surface once you remove the paint stain.
If the latex paint spots are very old and none of the previously mentioned cleaning solutions will remove the stains, use a strong chemical stripper designed to remove latex paint stains off aluminum surfaces. Brush the paint stripper on the aluminum and let it sit for several minutes before scraping it off with a plastic paint scraper. This process will remove any paint under the aluminum surface.